Automated control valves such as, for example, rotary control valves, are often used in process control plants or systems to control the flow of process fluids. A rotary control valve typically includes an actuator (e.g., a pneumatic actuator, an electric actuator, a hydraulic actuator, etc.) operatively coupled to a shaft extending from a rotary valve via a lever. The lever converts a rectilinear displacement of an actuator stem into a rotational displacement of the valve shaft. Thus, rotation of the lever causes the valve shaft and a flow control member (e.g., a disk, a ball, etc.) coupled to the valve shaft to rotate to increase or restrict the flow of fluid through the valve.
To couple the lever to the actuator stem, a rod end bearing is typically employed. The rod end bearing may include an internally threaded bore (i.e., a female connection) that threadably receives an externally threaded end (i.e., a male connection) of the actuator stem. Alternatively, the rod end bearing may include an externally threaded end that threadably couples to an internally threaded bore of the actuator stem. In either case, the externally threaded portion of the rod end bearing and/or the actuator stem is typically formed by machining bar stock. However, for typical bar stock, the cold-worked, high strength material is concentrated near the outer portion of the bar stock, which is usually machined away during formation of the externally threaded end (e.g., the externally threaded end of the rod end bearing or, alternatively, the externally threaded end of the actuator stem). As a result, the externally threaded end is typically formed from the softer, weaker material near the core of the bar stock.